Field of the Invention
The present invention relates to a method for depositing an aluminizing coating on a substrate.
Description of the Related Art
Aluminum-based coatings, called “aluminizing coatings,” are used to protect the surface of parts operating at high temperatures and in oxidizing environments. Such a coating may also serve as a fastening layer for attaching to another protective coating, said protective coating being more able to adhere to such an aluminizing coating than to the surface of the part itself.
For example, such parts are found in aeronautic turbojet engines, such as airplane engines. These parts are in particular turbine vanes or nozzles.
These parts are for example made from nickel-based superalloys.
To perform an aluminizing coating on such a superalloy, a layer of platinum 20 is first deposited on the surface 11 of said superalloy that is the substrate 10. This step is illustrated in FIG. 2A.
A thermal diffusion treatment is then done intended to diffuse the nickel of the superalloy 10 in the layer of platinum 20, and the platinum in the superalloy 10. This step is illustrated in FIG. 2B. This diffusion thus makes it possible to bring the nickel toward the free surface of the layer of platinum 20. This diffusion is done in a vacuum enclosure at a high temperature, for example 1100° C., for two hours.
A thermochemical aluminizing treatment is then done that leads to the deposition of a layer of aluminum 40 on the layer of platinum 20. This step is illustrated in FIG. 2C. Following this deposition, PtAl2 compounds 50 form in the layer of aluminum 40 that are dispersed in said layer of aluminum. The diffusion step is essential to prevent the formation of a large quantity of PtAl2, which then groups together to form plates on the surface of the layer of aluminum 40 that decrease the effectiveness of the protection. In fact, owing to this diffusion step, the nickel that has diffused in the layer of platinum 20 diffuses in the layer of aluminum 40, where it forms NiAl compounds 60, which reduces the formation of PtAl2 and therefore the risk of the formation of PtAl2 plates on the surface of the layer of aluminum 40.
The drawback of this currently used method is that the diffusion treatment of the layer of platinum is long and costly.